Simple prediction formula for peak oxygen consumption in patients with chronic heart failure

Peak oxygen consumption (VO₂) is one of the strongest predictors of survival in patients with chronic congestive heart failure (CHF), but it is unavailable in most practices. Peak VO₂ < 14 mL/kg/min identifies patients who might benefit from referral to a specialized CHF center. Accordingly, the current study was undertaken to derive a prediction formula based on routine stress data obtained from patients referred for cardiopulmonary exercise tolerance testing (CPETT). Subsequently, the prediction formula was validated in a separate cohort of similar patients referred for CPETT at another institution. The derivation cohort consisted of 208 patients with a diagnosis of CHF with reduced systolic function (left ventricular ejection fraction < 40%) who underwent elective CPETT. A multiple linear regression analysis was performed on available treadmill testing variables. A simple prediction formula was derived: Predicted peak VO₂ = 16.7 - 1.3 (sex) - 3.8 × (New York Heart Association functional class) + 0.04 × (peak heart rate) + 0.92 × (estimated metabolic equivalents). The validation cohort consisted of 112 patients referred for CPETT at a different institution for the evaluation of advanced CHF. The predicted peak VO₂ as obtained by the prediction formula was compared to the actual peak VO₂ using a Pearson coefficient of correlation. The predicted peak VO₂ was well correlated with the actual peak VO₂ demonstrating a correlation coefficient of r = 0.77 with a 95% confidence interval of (0.68-0.83). A simple prediction formula using four variables that are routinely obtained in standard exercise treadmill testing can identify patients in whom formal CPETT is advisable and facilitate early referral to specialized heart failure centers.